


Professional Reasons

by NothingSoDivine



Series: Strictly Professional [1]
Category: Fullmetal Alchemist: Brotherhood & Manga
Genre: Anal Fingering, Anal Sex, Casual Sex, Dominant Riza Hawkeye, Don't worry, F/M, I mean I tagged this for casual sex AND mutual pining, I was just really excited that I could tag him as a character, I'm absolutely going to keep doing that and nobody can stop me, I'm still very proud of it, Masturbation, Mutual Pining, My First Work in This Fandom, Pegging, Sex Toys, Sex for Professional Reasons, Strap-Ons, Submissive Roy Mustang, WUZZLES!, but I'm not tagging them because they're only implied, he does not get involved in anything, i guess? sort of, i wrote this in one day, implied previous relationships, mostly spoiler-safe, the dog stays in the living room, you know what you're getting yourselves into here
Language: English
Status: Completed
Published: 2020-10-21
Updated: 2020-10-21
Packaged: 2021-03-09 03:21:05
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 7,536
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27137215
Author URL: https://archiveofourown.org/users/NothingSoDivine/pseuds/NothingSoDivine
Summary: “You offered to fuck me in the ass for entirely professional reasons.”“Yes, sir.”
Relationships: Riza Hawkeye/Roy Mustang
Series: Strictly Professional [1]
Series URL: https://archiveofourown.org/series/1980829
Comments: 18
Kudos: 67





	Professional Reasons

**Author's Note:**

  * For [lbk_princen](https://archiveofourown.org/users/lbk_princen/gifts).



> so basically some nerdface messaged me at half past midnight on tuesday with a take so hot it kept me up for an hour drafting it in my head. then I got up for my 8:30am class and started writing and basically didn't stop until 9:30 that night.
> 
> this is functionally spoiler-safe and also I've been told I'm the only one who still cares about FMA spoilers so whatever, I guess.

They were walking down the hall together, Riza half a step behind, when Colonel Mustang sighed heavily and muttered, “God, I really need to get fucked.”

It was a testament to Riza’s self-control that she didn’t even lose her stride. “I beg your pardon, sir?”

She couldn’t see his face, but she saw the back of his neck flush red. “Nothing, Lieutenant. Forget I said anything.”

“Yes, sir,” said Riza.

* * *

She didn’t forget about it. It sat in the back of her head all day, and whenever she had a moment to think, it surfaced, and she chewed on it.

* * *

They were almost finished dinner when Riza blurted out, “Did you mean it?”

“Mean what?” Colonel Mustang asked.

“You said earlier that you needed something,” Riza continued, staring determinedly at her coffee. “Did you mean it?”

“I thought I told you to forget—”

“Because I could do that,” Riza interrupted before she could second-guess herself.

The Colonel’s coffee cup hit the table distinctly harder than usual. “What.”

Riza took a sip of coffee, willing her face to go back to its normal colour. She _never_ blushed. “I, er. I have the... equipment. To make that happen. Sir.” She took another long sip of coffee. She didn’t dare look up.

“Are you propositioning me, Lieutenant?”

Riza’s heart was doing some sort of gymnastic routine. “Did you want to be propositioned?” she countered into her mug.

Colonel Mustang drained his coffee. “Meet me in my office at 2100 hours,” he ordered, getting to his feet, and Riza felt sudden heat pool in the pit of her stomach. _Oh, god_.

“Yes, sir.”

“Lieutenant?” Mustang added, his voice sharp, and Riza managed to look up at him. His face was utterly unreadable. “I’m not agreeing to anything yet.”

“Yes, sir,” Riza managed faintly.

* * *

At 8:57, Riza rapped her knuckles on Colonel Mustang’s office door.

“Come in,” came the reply. She took a deep breath and obeyed.

“Colonel Mustang, sir. You wanted to see me.”

Mustang gave her a look from over his woven fingers, and oh god, the heat in that look made Riza weak all over, but she stood her ground. “I rather believe _you_ wanted to see _me_ , Lieutenant.”

The image flashed through Riza’s mind of Colonel Mustang naked in her bed, sweaty and disheveled and writhing under her as she — she forced it down, swallowed hard, licked her suddenly dry lips. “I suppose you could say that, sir.”

Mustang was still watching her with those dark eyes. “Were you serious?”

It took all of Riza’s self-control to hold his gaze. “Yes, sir.”

Mustang took a deliberate breath. When he released it, it trembled. Part of Riza was soothed by the knowledge that she was affecting Colonel Mustang too, and not just the other way around. The rest of her wrestled with the mental image of that breath against her ear. “I see,” he said.

Riza held her tongue.

Eventually, Colonel Mustang stood up. “I have some... concerns,” he said, stepping around his desk.

“Of course, sir.” Riza’s heart sank a little at the words, but she held it steady as best she could. Having concerns was not a rejection.

“I am your commanding officer,” Mustang continued, moving past Riza to open his book cabinet and stare at its contents. “I am your superior. We are not equals.”

“I am aware, sir.” Painfully so.

“I can’t afford to lose my best man — so to speak — because we tried to make it personal,” Mustang explained, and there was something very tender in his voice. Riza took a steadying breath. _Mustang called her his best man_.

“I didn’t offer to make it personal,” she said, cleared her throat. “Sir.”

Mustang turned back to her, making eye contact for which she was entirely unprepared. “You offered to fuck me in the ass for entirely professional reasons,” he said dryly, and Riza felt heat lance through her again. God, even if he turned her down, it would be worth it for the memory of hearing him say that — professional reasons. Right.

“Yes, sir.”

A smile tugged at the corner of Colonel Mustang’s mouth. “I see.”

Riza didn’t think she’d be able to hold his gaze much longer without her face bursting into flames, but thankfully he looked away and considered his bookshelf some more. “You said you had equipment,” he said, and Riza released in a rush the breath she hadn’t realized she’d been holding. Emotions went flooding through her — relief, hope, anticipation, others she couldn’t name fast enough.

“I did, sir,” she said. “I do.”

“What... kind of equipment?” Mustang asked.

Riza hesitated. She had no idea how to communicate that no, she hadn’t strictly done it with a man before, but yes, she knew what she was talking about, and yes, she had everything she needed. “How do you mean, sir?”

Mustang glanced over at her out of the corner of his eye. “I won’t have you putting gun oil on my unmentionables,” he said.

Riza stifled a startled laugh. “I have all the _proper_ equipment, sir.”

Mustang looked at her a little more consideringly. “Have you, now.”

Oh god oh god oh god. Those eyes were absolutely going to be the death of her. “Yes, sir.”

Mustang looked back at his books for a long moment, his graceful gloved fingers tracing the handles on the cabinet door. Then he huffed out a breath and closed the cabinet with a _tink_. “Very well then. Your place, I presume?”

All the strength went out of Riza’s knees as heat went flooding down her spine. “Yes, sir,” she said, voice suddenly throaty, and when Mustang turned to look at her, the look in his eyes was hot and molten. He almost looked angry, but Riza knew better.

“After you,” he said, gesturing to the door, and Riza managed somehow to remember how to walk.

Colonel Mustang held the door for her, and Riza thanked him with a nod. She dared not open her mouth to speak for fear she’d say something wrong and Mustang would change his mind.

They strode down the hall, side by side, in heavy silence. Riza’s head was spinning. Colonel Mustang had agreed to — he was going to let her — she couldn’t even think it, not here, not now. It seemed so improper in the bright artificial lights of the hallway, with all their colleagues rushing around them. As they rounded a corner, Mustang put a hand on her back, just the lightest brush of his gloved fingertips against her shoulder blade, and her skin tingled under his touch like it was remembering being on fire.

When they stepped outside, Mustang dropped his hand, and Riza felt suddenly bereft of something much greater. “I need to head home,” he said, checking his watch. “I’ll meet you where we agreed in forty-five minutes.”

Forty-five minutes. Riza nodded sharply. “Yes, sir.”

Mustang caught her eye. “Drive safe,” he said, and this time more than any other Riza felt how keenly he meant it.

“Yes, sir,” she said, holding eye contact until Mustang broke it to turn away and jog down the steps.

* * *

The trip home was a blur. Riza stumbled up the stairs to her apartment in a daze and let herself in. Black Hayate greeted her with cheerful enthusiasm, as always, but she was too distracted to return it. She gave him a scritch behind the ears and locked the door behind her before heading directly to her bedroom.

Her uniform went on a hanger in the closet, and she found herself fretting over what to replace it with. God, this was ridiculous. Colonel Mustang didn’t care what she was wearing. This wasn’t a date. It was... something else. Not a date. Muttering under her breath — “It’s not a date, Riza, it’s not a date” — she tossed on a pair of comfortable pants and an old white shirt and went to the bathroom to freshen up.

After washing her hands and giving her face a splash with the coldest water her sink provided, Riza returned to her bedroom and opened the bedside table. Everything she needed was in its proper place. She retrieved the unlabelled bottle of lubricant first, setting it on the table with all the nonchalance she could muster. The leather dildo was stashed safely in its drawstring bag; fluttery with nerves, Riza pulled it out and set it upright next to the lube. Both of them had seen quite a bit of use, and some of it recently; Riza very carefully didn’t think about it as she reached into the very back corner of the drawer to retrieve her harness. It was a tangle of leather straps and nickel-plated hardware that still shone despite the fine film of dust. She’d had to get it and the dildo custom-made from a leatherworker an inconvenient walking distance from the Academy, but they had been worth the hassle and expense. With the harness in one hand, Riza retrieved a soft cloth from the leather care kit in the bottom of her closet and sat down on the end of her bed.

When Colonel Mustang knocked on her door, Riza had just finished working oil into the leather straps of the harness. She rushed to answer, wiping her hands on the rag she’d grabbed for that purpose before almost running to open the door. When she opened it, her breath caught in her throat.

Colonel Mustang stood there in civilian clothes that made Riza’s mouth go suddenly dry. Her eyes raked down him, drinking in every glorious detail. He was in a slightly rumpled shirt and trousers, with a thin blue tie around his neck, a brown overcoat and a white scarf folded over his arm, and a pair of plain white gloves in one hand. When she realized she’d just given him a blatant once-over, her eyes darted back up to his face. His hair was damp, and she could smell soap and aftershave — good lord, had he taken the world’s fastest shower? His eyes were fixed on the tangle of leather straps in her free hand.

Riza cleared her throat, and Mustang’s eyes snapped to hers. “Colonel Mustang,” she greeted, stepping aside to let him in.

“Lieutenant Hawkeye,” he replied, breaking eye contact, and his words were formal but his tone had an undertone of sultry intimacy that made Riza want to wrap her thighs around him and squeeze. She shut the door behind him, staring at his back through the fine white linen of his shirt.

“I can take your coat,” she offered, and he handed it to her wordlessly along with his gloves as Hayate came bounding over to give Mustang a thorough sniff. He knelt to greet the dog, and Riza stepped around him to hang Mustang’s coat in the hall closet, tucking the gloves into one of its pockets and feeling acutely self-conscious about her clothing choices. _He doesn’t care, it’s not a date_ , she reminded herself, and took a steadying breath.

“You’ll have to excuse me for a moment,” she said, still facing the closet. “I have some preparations left to do. Please, make yourself comfortable out here.” She gestured to the living room.

“Of course,” said Mustang, following her gesture into the living room. Hayate bounded after him happily. “Take as much time as you need, Lieutenant.”

“Thank you,” she managed, skirting past him to the bedroom.

“And Lieutenant,” he added as she was closing the door, and she paused. When she met his eyes, they were briefly serious.

“I can leave at any time,” he said, and she flashed him the barest of smiles in acknowledgement before shutting the door.

She left the harness on the bed for the moment, tucking her leather care supplies back into the closet. In an attempt to steady her nerves, she took the care to put them back where they belonged; it helped, but not much. She closed the closet door firmly, then grabbed the empty water glass from her bedside table and went to fill it at the bathroom sink. She washed her hands, too, to make sure they were clean of the oil she’d used on the harness; she’d left her hair up, and she gave herself a critical look in the mirror above the sink before pulling it down, running a comb through it impatiently, and pinning it back up. _He doesn’t care how you look. It’s not a date_ , she reminded her reflection. Her eyes looked wide and nervous. She straightened her posture, set her shoulders, and took a steadying breath before grabbing the glass of water and returning to the bedroom.

She returned the glass of water to the bedside table, then regarded the harness on the bed. It was always at least a little bit awkward to get into, which wasn’t necessarily a bad thing on its own, but this didn’t feel like the time to be awkward about anything. This felt like the time to be confident and self-assured. Awkwardness felt too personal, and she’d promised not to make it personal. She picked up the harness.

It felt just as it always had, a steady, comfortable point of familiarity in an uncertain situation. She strapped the dildo into it and buckled the harness shut, enjoying the way it became an extension of her. There was always a moment where it shifted from being just a dildo to being Riza’s cock, and she hadn’t realized how much she enjoyed that until she suddenly returned to it after so long. She settled it into place, gave her bedroom a once-over, and opened the door.

Colonel Mustang was perched on the edge of the couch, petting Hayate with an enthusiasm that they both seemed to be enjoying immensely. Riza stood in the bedroom doorway with her feet planted, back straight, and shoulders set, and crossed her arms across her chest for lack of anything else to do with them. “Colonel Mustang,” she said sharply.

Mustang looked up immediately, damp hair falling into his eyes, and Riza saw his breath catch. “Lieutenant,” he breathed, like an incantation. His eyes were fixed on her cock, lips parted. The expression on his face could only be described as hunger. Riza shivered.

“Come here,” she said, and it came out like an order, but Mustang didn’t seem to mind. He rose to his feet immediately, and Hayate gave him an upside-down confused look as he crossed the room to stand in front of Riza. He was barely taller than she was; he must have taken off his shoes at the door while she was hanging up his coat. He stopped close enough to her that he had to look up at her face. She wasn’t sure what he saw there, but his eyes moved from one of her eyes, to the other, to her mouth, and back again, and he licked his lips. She wanted to kiss him, oh how she wanted to kiss him.

She stepped aside, and he entered her bedroom. She closed the door behind him with a soft _click_ , and she was close enough to see the shiver that went through him. She was standing right behind him. One tiny step and they’d be pressed together from shoulders to knees, her cock sliding between his legs—

She stepped around him and moved away, putting space between them so she wouldn’t do anything as stupid as try to embrace him. “Shirt, off,” she ordered, and Mustang’s hands went immediately to his tie. She watched him untie it deftly and drape it over the footboard, and then his fingers moved to his cuffs, flicking them open. She watched, mouth dry yet again, as he unfastened every button with military efficiency, and then he shrugged the shirt off and draped it next to his tie, leaving him in a sleeveless undershirt. His eyes only left her face to see where he would place each item.

“Trousers,” she ordered, a little breathless, and his hands went to his belt. Riza’s mind conjured up the image of that belt wrapped around his wrists and fastened to one of the sturdy bars of her headboard, and her eyes flicked up to the headboard in question for the slightest moment before she could stop them. Mustang followed her gaze just as briefly, but didn’t even free the belt from its loops, just opened it far enough to get to his fly. Riza tore her eyes away before Mustang shoved his pants off his hips, grabbing a sip of water from the glass on the endtable. When she turned back to him, Mustang was laying his socks over the footboard on top of his trousers. He turned back to her, straightening up, and Riza couldn’t stop her gaze from jumping downward. She could see the outline of Mustang’s hard cock through his underwear; the tip left a wet patch on the fabric. Riza swallowed hard. That was for her. She’d done that.

“Come here and turn around,” she managed, and Mustang did, giving her his back like he always did.

“Widen your stance a little.” He moved his feet so they were a little more than shoulder-width apart. _At ease, Colonel_ , she thought, but she wasn’t bold enough to say it. She just stepped up behind him, planted a hand between his shoulder blades, and forced him down to the bed.

Mustang made the most beautiful noise Riza had ever heard. He’d managed to catch himself with his hands, but had only really stopped himself from hurting his nose when he landed; his chest was against the coverlet and his ass was against Riza and she lost her breath when she realized he was flexible enough to bend that far with his legs straight. Her hand was still flat on his spine, and she was trembling with nerves. “Was that okay?” she asked, and her voice came out as a whisper.

“More than okay,” Mustang replied, turning his head so he could glance up at her. He was smiling. “I’m good. Are you good?”

“I’m good, as long as you’re good,” she said.

“I’m good. Keep going,” Mustang said, and looked away from her.

“Yes, sir,” she said under her breath, more to herself than anything else, and closed her eyes.

“Stay there,” she ordered, and Mustang made a muffled affirmative noise into the bedspread, so she removed her hand from his back to hook her fingers into the waistband of his underwear. He hadn’t been moving before, but he went very still at that; she hesitated, but Mustang nodded, and she slowly drew his underwear down over his hips. She felt the exact moment his cock sprang free, and winced. “Sorry,” she muttered.

“S’fine,” Mustang replied into the bed.

Riza slid Mustang’s underwear down to just below the point where his ass met his thighs and left it there. She had to pull back a little so her cock didn’t get caught, and she went to close the distance again but paused. She was terrified to touch him, she realized. The most she’d touched him so far was putting her hand on his back, and that was something she’d done a hundred times before, albeit for more wholesome reasons. She’d even avoided touching him just now, when she was stripping him. Her hands were visibly shaking, but she placed them on Mustang’s narrow hips.

Mustang’s skin shivered at her touch, goosebumps racing down his legs, and she heard him take a shaky breath. His skin was hot under her fingers — her hands must be cold, but Mustang didn’t pull away. If anything, he rocked infinitesimally back towards her. Riza kneaded at Mustang’s ass a little, almost absently, and used her thumbs to pull it apart so she could see his hole, and Mustang made a weak little noise and buried his face in the blanket.

 _Gorgeous,_ Riza thought, and reached for the lube.

Riza knew enough to be generous in wetting her fingers; as she rubbed them together to warm the lubricant, she admired Mustang’s ass like she’d never really had the chance to before. Quite apart from having never seen him naked, Riza had never felt like she was allowed to see him as a sexual being. She’d observed, in the sort of detached manner that seemed appropriate, that he was handsome, and much admired, and she’d been peripherally aware that he had presumably had sex before, but this was different. There was a world of difference between nebulous awareness and having someone in your hands. Riza wasn’t sure she’d ever be able to put this image out of her mind, of Colonel Mustang bent over her bed, as naked as she was ever likely to get him.

With her clean fingers, she held Mustang’s ass apart again to pour some lube directly on his hole, and Mustang gasped.

Riza shivered and set down the bottle of lube within easy reach. She’d have to replace it soon, she noted in the back of her mind; it was getting low. She ran her wet fingers across Mustang’s hole, and he made a beautiful noise that Riza wasn’t sure how to describe. “May I?” she asked, a little teasingly. It was reassuring to have gotten noises like that out of him; it made her feel a little less like she was the only one who wanted this more than she should.

Mustang made a choked noise. “Please,” he said, ever-so-casual, as though she was asking permission to speak up in a meeting, not finger his ass.

She slid one finger into him, and Mustang’s whole demeanour changed. He shuddered, moaning quietly, and his back relaxed into a sinuous arch. “Oh,” he said, and it sounded like pure, sweet relief. He tipped his head back, raising his face out of the blanket and raking his hair back off his forehead, rocking back against Riza’s hand. God, the way he _moved_. Riza would barely have recognized him, except that this was so clearly still Roy Mustang in front of her — but not Colonel Mustang, the Flame Alchemist; this was simply Roy, in a way Riza had never seen before. And, she realized, she might never see again; she crooked her finger slightly in the soft, wet clutch of Mustang’s ass and cherished the startled noise he made.

“Good?” she asked, and it seemed like an inadequate way to ask it, but feeling Mustang’s hole hot and tight around her finger was very distracting.

“ _Yes,_ ” he breathed, and the sound burned through Riza’s ears. That voice would haunt her at night; she knew there was no way she wouldn’t dream of it, wouldn’t picture Mustang leaning over her to breathe it in her ear every time she brought herself off until she forgot how it sounded.

“Good,” she repeated, and added her second finger.

Mustang moaned. Riza would never be able to look him in the face again after this. Her free hand was shaking and she wasn’t quite sure why; she used it to hold Mustang open, and his back slipped further into that gorgeous arch, pushing his ass up towards her hands. She fucked her fingers into him, just gently, and got a pretty little shivery moan out of him in response. God, she was so wet, she realized with a rush of — was that shame, or just embarrassment? _It’s not personal_ , she told herself, breathing deeply, and kept moving her fingers. _Professional reasons. Professional my ass,_ she thought, and then: _Well, his ass, I suppose,_ but before she could laugh at her own joke, Mustang clenched around her fingers and startled a noise out of her that almost matched his own.

They both went still at that. Mustang’s breathing was uneven, but so was Riza’s. She cleared her throat, reached for the glass of water. “You good?” she asked once she’d wet her mouth.

“Yes,” said Mustang.

“Can I,” Riza started, but she’d moved her fingers out of habit and Mustang cut her off with a gasp; with some difficulty, she stopped lazily fucking his ass open. “Can I, uh. Move on?”

“If you like,” Mustang said, and that gorgeous sensuality was gone; the Colonel was back. “I’m enjoying this, but I’m definitely loose enough to take your cock now.”

Riza tightened her grip on Mustang with her free hand. God, there was something about the way he said such a filthy thing in such a casual tone. “You said earlier that I could take as much time as I needed,” she said, and her voice sounded strangely raw to her own ears.

“I did, and that still sta— _oh._ ” Mustang’s voice melted into a purr, and Riza kept moving her fingers. The lube made Mustang’s ass perfectly slick, and he was tight but hadn’t clenched even once to try and reflexively keep her out. It occurred to Riza that he must have had a lot of practice, and the images _that_ conjured up made her crook her fingers sharply. Mustang made a startled noise. His spine was melting back into that languid arch; Riza wanted to run her tongue down it, from the nape of his neck to where her fingers sank into him. She was so glad she’d had him leave his undershirt on.

“I think maybe I want to keep doing this for a bit,” she said, pulling her fingers most of the way out to press her fingertips against his rim, and Mustang moaned. “Since you’re enjoying it.”

“Okay,” Mustang choked out, and moaned again as Riza sank her fingers all the way back in.

They lapsed into relative silence for a while, nothing but the sounds of their breathing — Mustang’s harsh, Riza’s even — and Mustang’s soft vocalizations and the wet noise of Riza fingering him. Back in her Academy days, Riza used to love using her hands like this. Rebecca used to joke that if she wasn’t so secretive, every girl in their hall would have wanted to worship at the shrine of Riza’s hands, and although Riza would never have actually let them, some tiny part of her always liked the idea on a purely manual-labour level. She hadn’t realized how much she’d been missing it; she’d thought cleaning and maintaining her guns was enough to satisfy the desire to do things with her hands, but there was really nothing like fingering someone.

She could tell when the two fingers stopped being enough. Mustang’s ass was wet and easy, and he started making these little whimpering noises with every breath that sounded like they might have been involuntary. Riza didn’t want to push her luck by making him ask for more; she briefly contemplated adding a third finger, but reached for the lube instead, and realized with a pulse of arousal that she wanted Mustang to feel stretched by her when she slid into him. She stilled her fingers, and Mustang whined, trying to rock back against them, so she pulled them out completely.

“Be patient,” she chastised when Mustang gasped and wriggled his hips. She gave her fingers a cursory inspection out of habit — they looked wet, but clean; lord only knew what he’d gotten up to in that shower, and the thought made Riza’s mouth water.

“No,” said Mustang, and it sounded more like a reflex than an actual denial, so Riza ignored him in favour of slicking her cock with lube. Her nervousness was back, but she did her best to ignore that, too. She was going to fuck her boss. She was about to fuck Colonel Mustang in the ass, and she was out of practice and tired from a long day but she would not think about that, she absolutely would not.

Mustang’s legs were a little too long. “Can you spread these any wider?” she asked, tapping the inside of his ankle with her foot.

He tried. “No,” he said, and again, the Colonel was back; his spine straightened and his voice cleared and the luxurious attitude was nowhere to be found, even as he stayed bent over with his bare, wet ass in the air and his chest on the bed. He turned his head to talk to her when his back straightened, Riza realized absently; it must have been harder to tilt back when his spine wasn’t already curved that way.

“Okay, close them,” she said, stepping away, and when Mustang obeyed, his underwear slid down his legs to pool on the floor. Riza crouched to tug them away from him, and he stepped out of them to let her. Her head was almost perfectly on a level with his ass _don’t look up don’t look up_ and if she’d looked up she could have sunk her tongue into him. She didn’t. She grabbed his underwear off the floor and stood up to toss it over one bedpost, then wrapped her hand around Mustang’s hip.

“Open,” she ordered, and Mustang widened his stance but kept his knees straight, pressing his weight into the balls of his feet to cant his hips up, and oh. Oh wow. Riza ran her thumb along the edge of Mustang’s hole, and Mustang keened, spreading his legs just a bit wider and bringing him down to the perfect height for Riza to guide the head of her cock into him, so she did.

Mustang let out a sigh like the one Riza had gotten when she first slid her finger into him, but more so, and Riza listened — there was that achingly sweet relief, and this time there was satisfaction, too, and as Riza slid in a little further, Mustang rewarded her with a moan. “Yes,” he breathed, and Riza wanted to cry at how gorgeous he sounded. Then he squeezed around her, and she felt it in the way she stopped being able to move, and they stayed like that for a second. Then: “Fuck,” he groaned, and before Riza could react to how that word sounded in his voice, he relaxed and she slid the rest of the way into him and he yelped.

“Shit, I’m sorry, I’m so sorry sir, I—” Riza panicked, going to pull out, but Mustang let out a guttural groan and rocked back against her and said “ _Fuck_ ” again, so reverently that Riza thought maybe she was dead, or dreaming, or something, because Roy Mustang simply did not sound like that under any circumstances, except apparently he _did_ sound like that when he was getting fucked, and Riza had no idea how she was supposed to go back to a respectable professional distance after hearing what he sounded like when he was full of her cock.

“Move,” Mustang gasped, and Riza realized with a start that she’d gone completely still — “ _Please,_ ” and Riza gasped and started moving.

Mustang groaned again, rocking his hips, and they fell into a rhythm almost immediately. Riza’s mind was racing and couldn’t settle on any one point of focus: Mustang’s ass, his legs, his back, the movement of his shoulder blades, the way his hands grasped at the blanket, the sounds she was forcing out of him with every thrust, the impact of his hips against hers — it was all too much, all at once, and she had no idea where to leave her attention. She spared a thought to be grateful that, despite being years out of practice, fucking wasn’t very complicated; she’d feel it tomorrow, from her ankles to her chest most likely, but she couldn’t really mess it up at this point.

Riza’s entire right hand was still wet with lube; she wiped it on her pant leg and wrapped it around Mustang’s other hip, holding him open again with her thumbs, and on the next thrust the noise that came out of him was a breathy “ _Yes._ ” Riza stifled her own noise and kept going. This wasn’t for her, she reminded herself, although it might as well have been. She was so wet she wouldn’t have been surprised to find she’d soaked right through her pants.

“Harder,” Mustang gasped, “please, harder — _fuck, yes, just like that,_ ” and Riza bit her lip so hard she was worried she’d draw blood. Then Mustang propped one of his knees on the edge of the bed, and that must have gotten her deeper or something because his moans started winding higher and higher and one of his hands flew from the bedspread to his cock and he started jerking himself off with frantic motions and Riza was suddenly seized with a furious desperation to see his face. She released his left hip and reached down to his head, grabbing a fistful of his hair, and when she pulled his head back Mustang’s voice cracked, then broke completely and his moans dropped down to a coarse, guttural register that made Riza shudder.

“ _Fuck,_ ” Mustang growled.

“I want to see your face,” Riza hissed, low and with such intensity she surprised herself. “Let me watch you.”

For one perfect, electric moment, Mustang’s eyes met hers. Then he was gasping, “Fuck, please, _fuck me, Riza, fuck me,_ ” and his eyes squeezed shut but Riza didn’t care because he was shaking and coming and Riza never wanted it to end.

Eventually, he stilled, and Riza released his hair, soothing his scalp briefly with the tips of her fingers. She’d stopped moving, but couldn’t remember exactly when; she took Mustang by the hips and pulled out of him as gently as she could. He made a small, sweet noise that even after all that made Riza shiver. Then he put both his feet flat on the ground and his hands out in front of him and stretched like a cat. Riza couldn’t tear her eyes off him.

“Goodness, I needed that,” he said, and he sounded almost normal, but his throat was just wrecked enough to give it away. He arched his back the other way, and Riza could have sworn she heard his spine pop at least once; then he rolled with surprising grace over onto his back and pushed himself far enough onto the bed that he wouldn’t fall. Riza watched him, but only peripherally; her attention was caught by the mess he’d left behind on the bedspread. She felt him glance up at her and follow her gaze.

“Oh, dear. I’m sorry, Lieutenant, I wasn’t thinking—”

“It’s fine,” Riza interrupted, looking away and reaching for the buckle at her hip. “I can wash it. Have some water,” she added, gesturing to the endtable.

“Thank you,” Mustang murmured, taking a sip of the water as Riza stepped out of her harness and deposited the whole mess on the table.

“I expect you’ll need at least half of a shower after that,” Riza said, as Mustang set the water back down.

“That would be great, thank you,” Mustang said, and Riza heard where he cut himself off from reminding her again of the nature of their relationship. The unspoken _Lieutenant_ hung in the air between them.

Riza cleared her throat, tugging at her sleeve. “There are towels on the shelf in the bathroom,” she said, eyes darting from the filthy bedspread to the row of clothes on the footboard to the curtains on her window to the glistening dildo on her bedside table, looking anywhere and everywhere but at Mustang.

“Yes, of course,” Mustang said, and rose unsteadily to his feet. Riza wasn’t looking at him, but she still saw his posture shift from sex incarnate back to Colonel Mustang, and her own shifted in response. She closed her eyes as he passed her, in the vain hope that if she didn’t see him, she wouldn’t want him quite so desperately, but the scent of his sweat and his soap and his aftershave and _sex_ flooded her nose instead, and she throbbed with need. Right, ignoring herself wasn’t working; new plan, get Colonel Mustang out of her bedroom as quickly as possible so she could get herself off—

“I’ll leave the door unlocked, so you can come in and wash your hands,” said Mustang, stripping off his undershirt on the way around the bed and laying it on top of his other clothes.

Right. Fuck. She needed to wash her hands before she could touch herself. “Thank you, sir,” she said automatically, and Mustang left the bedroom door open behind him.

Riza waited until the water had been running for at least thirty seconds before she entered the bathroom, partly out of habitual respect for Mustang’s privacy and partly because she had no idea what her face looked like right then but she did not want the Colonel to see it. When she saw herself in the mirror, she knew she’d been right about that. She was flushed pink all the way down her neck, pupils wide, eyes dazed, and lips swollen from how much she’d been biting them. She washed her hands as fast as she could, splashed her face with cold water, and hurried out of the bathroom, trying not to think about Mustang just on the other side of the shower curtain, naked and wet and touching himself. She almost ran back to the bedroom, shutting the door behind her and throwing herself down on the bed.

She’d have to be quick about it; even if Mustang didn’t take a militarily efficient shower, he’d showered before he came over, so he wouldn’t take very long. Riza shoved her pants and underwear off and spread her legs, sinking two fingers into her pussy easily. She hissed in a breath through her teeth as she brought her other hand down to rub frantically at her clit. God, she was almost too wet to get herself off, and the sounds of her fingers made her shudder with how much it sounded like when she’d been fingering Mustang. She arched her back, pushing her hips up into her hands, and her eyes fell shut. Fuck, he’d sounded so beautiful; she remembered how easy it had been to slide her cock into him, crooked the fingers in her pussy, and came hard with a strangled cry.

She came down shivering. God, she’d needed that; she stretched her legs, removing her hands from herself and opening her eyes.

Colonel Mustang stood in the doorway, wearing a towel and a hint of a smirk.

Riza sat bolt upright, planting both hands on the coverlet before she remembered they were dirty. Oh, well; it needed washing anyways. “Colonel Mustang,” she blurted, feeling her face go red. “I—I’m sorry, I was just—”

“So you enjoyed yourself, too, then?” Mustang interrupted. His eyes had gone molten again, but at least they were on Riza’s face. He licked his lips. “So to speak.”

Riza swallowed hard. “Yes, sir,” she replied, then — “very much.” God, she needed to at least clean up a little before getting herself off again. And Mustang probably needed to leave.

Mustang smiled, and oh dear. Riza knew that smile. That smile meant trouble, and he was pointing it at her, with those molten eyes that got her so desperately hot. Whatever he was thinking, it was a bad idea, she knew it. He was her commanding officer, and they had important affairs to handle, and neither of them could afford to deal with the amount of trouble it would cause if one of those affairs was between the two of them—

“I’m glad,” he said, and stepped out of the doorway to let her by. Slowly, she stood up and walked past him; her thighs slid together. She needed a shower, too, but that could wait.

“Lieutenant,” Mustang called as she was entering the bathroom.

She stuck her head back out. “Yes, sir?”

He was smirking again. “My underwear is in dire need of a wash. Would it be all right with you if I left it here?”

Something about the idea of Mustang leaving something of his at Riza’s apartment put a warm glow behind Riza’s sternum. Then it occurred to her what else that meant, and she felt another pulse of wetness run down her thighs. Fuck. “Yes, sir. That’s fine.”

Mustang’s smirk widened briefly into a smile. “Excellent. Thank you, Lieutenant.”

He disappeared back into the bedroom, and she ducked into the bathroom to wash her hands again. By the time she emerged, Mustang was dressed and sitting on the couch again, tying his tie while Hayate played with his feet. When he saw Riza, he stood, adjusting his tie snugly up against his throat.

“Lieutenant,” he said.

She didn’t feel like his Lieutenant. She felt like she’d just had the best sex of her life and could go for another three rounds. She was wearing nothing but an old uniform shirt and her hair clip, and the insides of her thighs were wet almost to her knees. “Colonel,” she said.

He’d tucked his shirt back in and everything; he looked no more rumpled than when he’d arrived. “I should be off,” he said. “Early morning tomorrow.”

Riza glanced at the clock. It was almost a quarter past eleven. “Indeed,” she said. “It’s gotten quite late.”

Mustang headed for the door, and she followed him, watching his back like she always did, though the biggest threat right now was Hayate, collapsed in a heap on the living room floor. When he leaned down to grab his shoes, Riza reached into the closet to fetch his coat; she felt her shirt ride up, and felt Mustang’s eyes on her, but didn’t blush.

“Here you are,” she said, handing over his coat once he finished with his shoes. “Good night, Colonel. Drive safe.”

“Thank you,” Mustang said as she reached past him to open the door. He nodded to her as he passed, and she nodded back, stifling her smile so it wouldn’t split her face in two.

“Oh, and Lieutenant Hawkeye?” he said as she went to close the door.

She stopped. “Yes, Colonel Mustang?” she asked.

Mustang’s eyes were soft. He reached out and placed his hand on her shoulder; she felt the warmth of his skin through the one thin layer of her shirt, and goosebumps rising around it.

“Thank you,” he said, squeezing gently.

She had no idea so much feeling could fit into two syllables. “It was truly my pleasure, sir,” she replied, and relished the way that made the heat flare in his eyes. He nodded once, sharply, and turned away.

Riza closed the door with a heavy click and fastened both locks. Then she turned around and leaned against it. What an evening, she thought.

Then she thought about Colonel Mustang driving home with nothing on under his trousers, and pushed herself up off the door. She had a toy to clean.

* * *

For the longest month of Riza’s life, Mustang didn’t mention it. Everything went back to normal, and if not for the freshly conditioned state of her harness and the seemingly innocuous pair of men’s underwear sitting in the top drawer of her dresser, she’d almost start to believe it had been a dream. It certainly would have been in keeping with the state of her dreams recently.

Then, one day, she was lying flat on her stomach in the belfry of an old church with her sniper rifle beside her and phone in hand, and Mustang was on the other end of the line, saying, “Elizabeth, darling, how have you been?”

“Not bad,” she replied. “Business is slow today. We’re not expecting many customers.”

“Well, I suppose that’s bad news, but at least I get to spend more time on the phone with you!” Mustang gushed, and Riza rolled her eyes.

“I suppose so,” she said.

“I’ve been wanting to talk to you, actually,” said Mustang, and Riza pressed the phone to her ear, listening carefully. “You remember when we went on that date last month?”

Riza was briefly confused, trying to decode his statement. Then she realized — that wasn’t coded. He was talking about the time he let her fuck him. The memory sent warmth curling down her spine. “Oh! You mean that time I took you for dinner?” she said, as innocently as she could, and grinned when she heard Mustang cough.

“I was thinking I’d like to do something like that again,” he continued, and the heat coiling at the base of her spine spiked a little hotter. “Except maybe this time _I_ could take _you_ for dinner? I don't know if that's something you'd be interested in.”

Oh. _Oh._ “That sounds wonderful,” Riza said, letting her voice drop into sincerity for a moment. It came out as a purr. She could practically hear Mustang shudder on the other end.

“Excellent. I’ll pick you up tonight, then? Same time, same place? Oh, and if I’m stopping on the way, would you prefer flowers or chocolates?”

Was that code? Riza had an inkling of what he might mean by it if it was. They’d have to come up with so many new extensions to their code system. “Hmm. Might as well bring both,” she teased. “Just to be _safe_ , you know?”

“I do know,” said Mustang, and she got the distinct feeling he did. “See you tonight.”

“See you tonight,” she promised.

**Works inspired by this one:**

  * [Professional Reasons (Mustang Remix)](https://archiveofourown.org/works/27179929) by [NothingSoDivine](https://archiveofourown.org/users/NothingSoDivine/pseuds/NothingSoDivine)




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